1. Field of the Invention
This invention relates to automatic garage door operators, and more particularly to the control of the range of movement of door operators using adjustable limit switches.
2. Description of the Prior Art
Garage door operators are well known and are commonly used to open and close automatically upwardly acting overhead garage doors. These garage door operators, which are electric motor driven and usually remotely operated by radio control, provide considerable convenience to the motorist for powered, remote opening and closing of the garage door. The operators are usually actuated using a remote transmitting unit, which is typically carried in a vehicle, and is used to signal the controller of the garage door opener system to raise or lower the door, as the driver wishes.
Many different forms have been devised in the prior art to connect the door operator drive mechanisms to the garage door to be moved. Many garage doors are sectional garage doors of the overhead acting type which slide upwardly on a track to a position adjacent the ceiling of the garage. For these doors, the garage door operator includes a frame extending along the garage ceiling which provides a rail for a load carriage that moves longitudinally along the frame. A drive mechanism moves the load carriage, and in many instances, this drive mechanism includes a flexible drive member, and more particularly, a roller chain. The load carriage is pivotally connected to the top section of the sectional garage door. This same construction is also used with slab or one-piece garage doors which are pivoted to swing upwardly adjacent the garage ceiling when in an open position. In this manner, as the load carriage is driven back and forth by the drive mechanism along the frame, the garage door, which is attached to the load carriage, opens and closes.
It is necessary to stop the movement of the drive mechanism and the load carriage when the garage door has reached the fully opened or fully closed positions. For this purpose, limit switches have typically been provided adjacent to the frame. One limit switch was usually mounted along the forward end of the frame adjacent to the door, and this limit switch was engaged by the load carriage when the door was fully closed. Another limit switch was usually mounted along the other end of the frame adjacent to the drive train housing, and this limit switch was engaged by the load carriage when the garage door was fully opened. These limit switches provided an electrical signal when the load carriage had reached a desired opened or closed position, and this electrical signal was used by the controller of the garage door operator to halt the actuation of the drive mechanism.
Both of these limit switches needed to be adjustable along the length of the frame so that they could be set in any desirable position depending upon the size of the door and the geometry of the door travel. Due to varying geometries of garages, the position of the carriage when the door was fully opened or fully closed could not be preset, so the limit switches could be positioned at any desirable location along the frame to be engaged by the carriage when the door had reached the proper position. This feature prevented the limit switches from being securely fixed in place along the frame.
In order to engage the load carriage, these limit switches needed to be exposed. The location of the limit switches also required that each of the limit switches be connected to the controller within the housing by a length of wiring, and this wiring was also not fully protected. Furthermore, because the limit switches need to be adjustable, it is not easily possible to provide for a fixed protected enclosure for the limit switches or for the wiring. As a result, the limit switches and their wiring could be subjected to inadvertent or unintentional mistreatment, mishandling or abuse. Since the limit switches and the wiring were exposed in the garage ceiling, there was a possibility that they could be damaged. Furthermore, because the limit switches were intentionally adjustable, the limit switches could become loose and could be inadvertently moved from the desired set position. This inadvertent movement could result in undesirable incomplete opening or closing of the door and the need for readjustment. This required that limit switches be routinely monitored and adjusted to assure that they were in the proper position.
In addition, the positioning of the limit switches was a procedure that required a moderate amount of time or expertise. There was no automatic procedure for initially positioning the limit switches or for later re-positioning them if needed. The user or service technician would position the limit switches in a rough fashion and then adjust the position depending on the final movement of the door. This procedure required some expertise or necessitated repeated trial-and-error to position the limit switches in the precise desired position.